H264的level的计算方法

比如分辨率: 1920*1080, 参考帧率: 60的h264码流是哪个level呢

H.264的宏块大小为16×16 in H.264,每帧宏块的个数为分辨率除以16
max-fs = ceil( width / 16.0 ) * ceil( height / 16.0 )

计算得:8100

每秒宏块数量为每帧宏块数乘以帧率.
max-mbps =max-fs*参考帧率

计算得:486000

参考ITU. p. 324. "Recommendation ITU-T H.264"表格:

Levels with maximum property values [39]

Level	Max. decoding speed		Max. frame size		Max. video bit rate for video coding layer (VCL) kbit/s (Baseline, Extended and Main Profiles)	Examples for high resolution @ highest frame rate Toggle additional details
	Luma samples/s	Macroblocks/s	Luma samples	Macroblocks
1	380,160	1,485	25,344	99	64	128×96@30 176×144@15
1b	380,160	1,485	25,344	99	128	128×96@30 176×144@15
1.1	768,000	3,000	101,376	396	192	128x96@60 176×144@30 352×[email protected]
1.2	1,536,000	6,000	101,376	396	384	128x96@120 176×144@60 352×288@15
1.3	3,041,280	11,880	101,376	396	768	128x96@172 176×144@120 352×288@30
2	3,041,280	11,880	101,376	396	2,000	128x96@172 176x144@120 352×288@30
2.1	5,068,800	19,800	202,752	792	4,000	176x144@172 352×240@60 352×288@50 352×480@30 352×576@25
2.2	5,184,000	20,250	414,720	1,620	4,000	176×144@172 352×480@30 352×576@25 720×480@15 720×[email protected]
3	10,368,000	40,500	414,720	1,620	10,000	176×144@172 352×240@120 352×480@60 720×480@30 720×576@25
3.1	27,648,000	108,000	921,600	3,600	14,000	352x288@172 352x576@130 640x480@90 720×576@60 1,280×720@30
3.2	55,296,000	216,000	1,310,720	5,120	20,000	640x480@172 720x480@160 720x576@130 1,280×720@60
4	62,914,560	245,760	2,097,152	8,192	20,000	720x480@172 720x576@150 1,280×720@60 2,048×1,024@30
4.1	62,914,560	245,760	2,097,152	8,192	50,000	720x480@172 720x576@150 1,280×720@60 2,048×1,024@30
4.2	133,693,440	522,240	2,228,224	8,704	50,000	720x576@172 1,280×720@140 2,048×1,080@60
5	150,994,944	589,824	5,652,480	22,080	135,000	1,024×768@172 1,280×720@160 2,048×1,080@60 2,560×1,920@30 3,680×1,536@25
5.1	251,658,240	983,040	9,437,184	36,864	240,000	1,280×720@172 1,920×1,080@120 2,048×1,536@80 4,096×2,048@30
5.2	530,841,600	2,073,600	9,437,184	36,864	240,000	1,920×1,080@172 2,048×1,536@160 4,096×2,160@60
6	1,069,547,520	4,177,920	35,651,584	139,264	240,000	2,048×1,536@300 4,096×2,160@120 8,192×4,320@30
6.1	2,139,095,040	8,355,840	35,651,584	139,264	480,000	2,048×1,536@300 4,096×2,160@240 8,192×4,320@60
6.2	4,278,190,080	16,711,680	36,651,584	139,264	800,000	4,096*2,304@300 8,192×4,320@120

 

根据每秒宏块数,来查对应表格.
Level 4.1
VBV maximum bit rate [1000bits/s] 50Mbit/s
Macroblocks/s 245760
Resolution and frame rate 1920×1088@30 or 2Kx1K@30

Level 4.2
VBV maximum bit rate [1000bits/s] 50Mbit/s
Macroblocks/s 522240
Resolution and frame rate 1920×1088@60 or or 2Kx1K@60

可见486000在Level 4.1和Level 4.2之间,所以Level是4.2, Level的确定原则是找<=的关系.